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View data via LAS (monthly means, view daily data at "choose dataset -> NCEP Reanalysis")
Data access via file system: /data/icdc/reanalyses/ncep_reanalysis1
The National Centers for Atmospheric Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) have accomplished different re-analysis projects which aim on the generation of global data sets for a long time period for different atmospheric parameters. The here presented NCEP1 reanalysis has been used in numerous publications and has, therefore, in addition to the recent re-analysis products the advantage of very long time series.
The re-analysis is created with a model similar to the one used for weather forcasts. This model is initialised with measured data from different sources, including observations from weather stations, ship, aircraft, radiosondes, and satellite. Using one model for the whole re-analysis period generates homogeneous data that can be used for long term studies.
NCEP/NCAR has produced several re-analyses, that are described on their web-page. Here we give an introduction to the NCEP/NCAR Reanalysis I (1948-present). This free data set is updated continuously and has therefore many users worldwide. There is a large number of available parameters in several height levels, NCEP divided into 7 groups on its website, after level or properties:
- Pressure level
- Surface Fluxes
- Other Fluxes
- Derived Data (for example monthly means)
- Spectral Coefficients
Using the NCEP search funktioncan also be convenient to search for parameters in various data sets. ICDC has a selection of ground-level parameters put together, which are listed in the following table.
|Air temperature (air)||K||2 m|
|Minimum Temperature (tmin)||K||2 m|
|Maximum Temperature (tmax)||K||2 m|
|Latent Heat Net Flux (lhtfl)||W/m^2||Surface|
|Net Longwave Radiation Flux (nlwrs)||W/m^2||Surface|
|Relative humidity (rhum)||%||Surface (0.9950 sigma level)|
|Sensible Heat Net Flux (shtfl)||W/m^2||Surface|
|Volumetric Soil Moisture (soilw)||fraction||between 0-10 cm below ground level|
|Soil Temperature (tmp)||K||between 0-10 cm below ground level|
|Specific Humidity (shum)||kg/kg||2 m|
|Convective Precipitation Rate (cprat)||Kg/m^2/s||Surface|
|Surface Pressure (pres)||Pa||Surface|
|Total cloud cover (tcdc)||%||Entire Atmosphere Considered As a Single Layer|
|u-wind (uwnd) and v-wind (vwnd)||m/s||10 m|
Period and temporal resolution:
- 1948/01/01 to now
- 6-hourly, daily and monthly
Coverage and spatial resolution:
- Spatial resolution: about 1.875° x 1.875°, Gaussian grid, (for some parameters 2.5° x 2.5°)
- Geographic longitude: 0.0°E to 358.125°E
- Geographic latitude: -88.542°N to 88.542°N
- Dimension: 192 columns x 94 rows (for some parameters 144 x 72)
Four categories are defined by Kalnay et al. (pdf, not barrier-free):
- A is for variables that are mainly influenced by observational data. These variables have the best quality.
- B is for variables that are influenced by observational data and dependent on the model. They have less quality than A.
- C is for variables that are not directly influenced by observations but solely based on the model. They are less reliable.
- D is for variables that are not from the model but from external sources, like for example the land-sea-mask.
The NCEP/NCAR Reanalyse Problem List contains all known problems related to the re-analysis data sets.
Remon Sadikni, ICDC
Physical Sciences Division: Data Management
Boulder, CO 80305-3328https://www.klimacampus.de/?id=
- Kalnay et al (1996)
- Jakobson et al. (2012) (pdf, not barrier-free)
- Serreze et al. (2012) (pdf, not barrier-free)